1. Field of the Invention
The present invention relates to a recording apparatus and, more particularly, to a so-called serial type recording apparatus for moving a recording means along a recording medium.
Recording apparatuses include a portable calculator, a portable electronic typewriter, a facsimile machine, a copying machine, and a printer. A recording means is exemplified by a system using a thermal recording type or scheme such as a thermal or heat transfer scheme, a system using an ink-jet recording scheme such as a bubble jet scheme, and a system using an impact recording scheme such as a daisy wheel or wire dot scheme.
2. Description of the Related Art
A recording apparatus using a disposable ink cartridge of a bubble jet scheme is exemplified as a conventional recording apparatus of this type, as shown in FIGS. 1 to 6.
The overall arrangement of the recording apparatus will be described with reference to FIGS. 1 and 2. A recording apparatus R includes a frame 1 as a housing. A base (to be referred to as a chassis hereinafter) 2 is fixed in the frame 1 to support a stepping motor 7 (to be described later), a pinch roller 3 in FIG. 2, and the like. A guide shaft 4 is fixed to the frame 1 at both its ends and movably guides a carriage 5. Part of a timing belt 6 is locked with the carriage 5, and the timing belt 6 is driven by the stepping motor 7. The carriage 5 and a recording head 8 mounted on the carriage 5 are driven by the timing belt 6 along a recording sheet 11 upon rotation of the timing belt 6 by a driving force of the stepping motor 7. Ink is discharged from the recording head 8 to record information on the recording sheet 11. A lever 8a is a head press/release lever.
A feed roller 9 feeds to a recording position the recording sheet 11 inserted from an insertion port 10 as shown in FIG. 2. An elastic body is mounted on the surface of the feed roller 9 to prevent slippage of the sheet. The feed roller 9 is also driven by the stepping motor 7 during sheet feeding in this embodiment. The sheet 11 is clamped between the feed roller 9 and the pinch roller 3 and is then fed. A platen 12 can hold the recording sheet 11 at the recording position. A flexible cable 13 supplies a recording signal to the recording head 8 mounted on the carriage 5. A home position sensor 14 senses the carriage 5 when the carriage 5 reaches the home position.
Driving systems of the timing belt 6 and the feed roller 9 upon driving of the stepping motor 7 will be described with reference to FIGS. 3 to 5.
Referring to FIGS. 3 and 4, a worm wheel 22 is fitted on a feed roller shaft 21 to rotate the feed roller shaft 21 only in one direction, as will be described later. An arbor 23 is fitted and fixed on the roller shaft 21. A spring clutch 24 is hooked between the arbor 23 and the worm wheel 22. One end of the spring clutch 24 is locked in a groove 22a of the worm wheel 22 and is rotated together with the worm wheel 22. When the worm wheel 22 is rotated by the stepping motor 7 in the E direction (during recording) shown in FIG. 4 in a manner to be described later, the spring of the spring clutch 24 is not engaged with the arbor 23, and the feed roller 9 and the roller shaft 21 are not rotated. Only when the worm wheel 22 is rotated in the F direction (during sheet feeding), the spring of the spring clutch 24 is engaged with the arbor 23, so that the feed roller 9 and the roller shaft 21 are rotated in the F direction.
Referring to FIG. 3, a belt driving pulley 25 is rotated by the stepping motor 7 to drive the timing belt 6. A worm gear 26 is rotated by the stepping motor 7 and is meshed with the worm wheel 22. The belt driving pulley 25 and the worm gear 26 are illustrated as if they overlap each other. However, the belt driving pulley 25 and the worm gear 26 are integrally mounted on the shaft of the stepping motor 7, as shown in FIG. 6. Therefore, the belt driving pulley 25 and the worm gear 26 can be simultaneously driven by the stepping motor 7.
A structure associated with the pinch roller 3 will be described with reference to FIGS. 2, 3, and 5. Referring to FIGS. 2, 3, and 5, a pinch roller shaft 31 is made of a conductive material in the same manner as the pinch roller 3. Both end portions of the pinch roller shaft 31 are held by guide grooves 1A of the frame 1. The roller shaft 31 is biased between both the end portions and the pinch roller 3 toward the feed roller 9 by a spring portion 32 extending from the chassis 2 of a conductive material toward the roller shaft 21.
An operation of the recording apparatus having the above structure will be described below.
Before the start of recording, a corner 5A of the carriage 5 shown in FIG. 4 abuts against the home position sensor 14 and is stopped upon detection of the stop state by the sensor 14. When a character-feed signal for moving the carriage 5 is supplied to the stepping motor 7 to perform recording, the motor 7 is rotated in a direction indicated by an arrow A (FIG. 4) to rotate the worm gear 26 together with the belt driving pulley 25. Although the worm wheel 22 is rotated in the E direction by the worm gear 26, as described above, the spring clutch 24 shown in FIG. 3 is disengaged from the arbor 23. The roller shaft 21 mounted with the arbor 23 is not rotated. Therefore, sheet feeding by the feed roller 9 is not performed.
Upon rotation of the belt driving pulley 25 in the A direction of FIG. 4, the carriage 5 is moved in a direction indicated by an arrow C. Meanwhile, an ink discharging signal is selectively supplied to the recording head 8 through a flexible cable 13 in synchronism with a character-feed signal input to the motor 7. When the ink supplied from an ink cartridge is discharged from the recording head 8, information is recorded on the recording sheet 11. The timing belt 6 is looped between the driving pulley 25 and idler pulleys 28A, 28B, and 28C.
When recording is completed, the stepping motor 7 is rotated in the reverse direction to cause the carriage 5 to return to the home position sensor 14, i.e., in the D direction. More specifically, the stepping motor 7 is rotated in the B direction to rotate the worm gear 26 and the belt driving pulley 25. Upon rotation of the worm gear 26 and the pulley 25, the worm wheel 22 is rotated in the F direction (FIG. 4). During rotation of the worm wheel 22 in the F direction, the spring clutch 24 shown in FIG. 3 is engaged with the arbor 23 to rotate the roller shaft 21 in the F direction. Therefore, the sheet 11 is fed by the feed roller 9. In other words, the sheet 11 is fed during returning of the carriage 5, i.e., during non-recording.
In the conventional recording apparatus described above, a sheet feed amount of each cycle is determined by a rotational amount (rotational angle) of the stepping motor 7, i.e., a rotational amount for returning the carriage 5. Even if recording with a full width is not performed, the carriage 5 must be moved to the left end of the frame 1 shown in FIG. 5, and the sheet 11 is fed during the return stroke of the carriage 5 to the home position.
When continuous sheet feed operation is required, recording is interrupted every one-character sheet feeding, and the carriage 5 must be moved to the left end of the frame 1. In addition, the sheet feed speed is not changed, and therefore the continuous sheet feed speed is undesirably low.
In sheet feeding for loading the recording sheet 11 in the recording apparatus R, the carriage 5 repeats reciprocal movement. If a liquid spray recording head such as an ink-jet or bubble jet recording head is used, an ink discharging surface of the head 8 is brought into contact with the leading end of the recording sheet 11 to contaminate the recording sheet 11. In addition, paper dust may be attached to the ink discharging surface, thus impairing the ink discharging function and recording quality.